A laser two focus velocimeter with high spatial resolution usingconfocal optical system

摘要

Measurement of flow velocity using optical techniques hasadvantages to measure flow velocity in a microscopic region withoutdisturbing it. However the decrease of the depth of the measuring region(the length of the measuring region) is very difficult in the opticaltechniques. In this study a new velocimeter with high spatial resolutionis proposed. The velocimeter was based on a laser two focus velocimeter(L2F) and its optical system was constructed with a confocal system todecrease the depth of the measuring region. The advantage of theconfocal optical system is that the light from the only part within thefocal region is detected strongly. The depth of the measuring region ofproposed L2F was about 10 μm. The reliability of the L2F with theconfocal system was confirmed by measuring velocities of moving atungsten wire. The results of experiments show that the proposed lasertwo focus velocimeter using the confocal optical system achieved thevelocity measurement with high spatial resolution and it is extremelyeffective instrument to measure the flow velocity in microscopic regions